An evolution of a wireless access scheme and a wireless network of a cellular mobile communication (hereinafter, referred to as Long Term Evolution (LTE)” or Evolved Universal Terrestrial Radio access (EUTRA)”) has been standardized in a 3rd Generation Partnership Project (3GPP). In LTE, an Orthogonal Frequency Division Multiplexing (OFDM) scheme, which is multicarrier transmission, is employed as a communication scheme of wireless communication from a base station apparatus to a mobile station apparatus (referred to as downlink (DL)). Further, in LTE, Single-Carrier Frequency Division Multiple Access (SC-FDMA), which is single carrier transmission, is employed as a communication scheme of wireless communication from the mobile station apparatus to the base station apparatus (referred to as uplink (UL)). In LTE, a Discrete Fourier Transform-Spread OFDM (DFT-Spread OFDM) scheme is employed as the SC-FDMA scheme.
In order to meet the demand, Long Term Evolution-Advanced (LTE-A), which at least supports the same channel structure as that of LTE, is considered. A channel is a medium used for transmission of signals. A channel used in a physical layer is called a physical channel, whereas a channel used in a Medium Access Control (MAC) layer is called a logical channel. Examples of types of physical channel include a Physical Downlink Shared CHannel (PDSCH) used in transmission and reception of data and control information of the downlink, a Physical Downlink Control CHannel (PDCCH) used in transmission and reception of control information of the downlink, a Physical Uplink Shared CHannel (PUSCH) used in transmission and reception of data and control information of the uplink, a Physical Uplink Control CHannel (PUCCH) used in transmission and reception of control information of the uplink, a Synchronization CHannel (SCH) used for synchronization establishment of the downlink, a Physical Random Access CHannel (PRACH) used for synchronization establishment of the uplink, a Physical Broadcast CHannel (PBCH) used in transmission of system information of the downlink, and the like. The mobile station apparatus or the base station apparatus assigns signals which have been generated from control information, data, and the like to each physical channel and transmits the signals. Data which is transmitted on the physical downlink shared channel or the physical uplink shared channel is called a transport block.
Control information which is mapped on the physical uplink control channel is called Uplink Control Information (UCI). The uplink control information is control information (reception confirmation reply; ACK/NACK) indicating Acknowledgement (ACK) or Negative Acknowledgement (NACK) concerning data assigned to the received physical downlink shared channel, control information (Scheduling Request: SR) indicating a request for allocation of an uplink resource, or control information (Channel Quality Indicator: CQI) indicating reception quality (also referred to as channel quality) of the downlink.
<Cooperative Communication>
In LTE-A, in order to reduce or suppress interference in the mobile station apparatus in a cell edge region or to increase reception signal power, Cooperative Multipoint communication (CoMP communication), which performs communication between adjacent cells in cooperation with each other, is being considered. Note that, for example, the form in which the base station apparatus performs communication using a certain frequency band will be referred to as a “cell”. For example, as the CoMP communication, in a plurality of cells, a different weighting signal process (pre-coding process) is applied on a signal, a plurality of base station apparatuses cooperate to transmit the signal to the same mobile station apparatus (also referred to as Joint Processing or Joint Transmission). This method can improve the signal power-to-interference noise power ratio of the mobile station apparatus and improve the reception performance of the mobile station apparatus. For example, as CoMP communication, a method in which a plurality of cells cooperate to perform a scheduling for the mobile station apparatus (Coordinated Scheduling: CS) is being considered. This method can improve the signal power-to-interference noise power ratio of the mobile station apparatus. For example, as CoMP communication, a method in which a plurality of cells cooperate to perform beamforming on signals and transmit the signals to the mobile station apparatus (Coordinated Beamforming: CB) is being considered. This method can improve the signal power-to-interference noise power ratio of the mobile station apparatus. For example, as CoMP communication, a method in which only one cell transmits signals using a predetermined resource, and other cells do not transmit signals using the predetermined resource (Blanking and Muting) is being considered. This method can improve the signal power-to-interference noise power ratio of the mobile station apparatus.
In addition, with respect to a plurality of cells used in cooperative communication, different cells may be configured by different base station apparatuses, different cells may be configured by different Remote Radio Heads (RRH) (more compact outdoor radio unit than the base station apparatus, and also referred to as a Remote Radio Unit: RRU) which are managed by the same base station apparatus, different cells may be configured by a base station apparatus and an RRH managed by the base station apparatus, and different cells may be configured by a base station apparatus and an RRH managed by another base station apparatus different from the base station apparatus.
A base station apparatus having a wide coverage is generally referred to as a macro base station apparatus. A base station apparatus having a narrow coverage is generally referred to as a pico base station apparatus or a femto base station apparatus. The RRH generally operating in an area having a narrower coverage than that of the macro base station apparatus is considered. The deployment of a communication system including the macro base station apparatus and the RRH, and in which the coverage supported by the macro base station apparatus includes all or a part of the coverage supported by the RRH is referred to as a heterogeneous network deployment. In a communication system of such a heterogeneous network deployment, a method is considered in which the macro base station apparatus and the RRH cooperate to transmit signals to the mobile station apparatus located within an overlap coverage. Here, the RRH is managed by the macro base station apparatus and transmission and reception thereof are controlled. In addition, the macro base station apparatus and the RRH are connected to each other by a wired line such as an optical fiber and/or a wireless line using a relay technology. In this manner, since the macro base station apparatus and the RRH performs cooperative communication using the same radio resource as a whole or partially, it is possible to improve overall frequency utilization efficiency (transmission capacity) within an area of a coverage of the macro base station apparatus.
When the mobile station apparatus is located in the vicinity of the macro base station apparatus or the RRH, the mobile station apparatus can perform single cell communication with the macro base station apparatus or the RRH. In other words, some mobile station apparatuses perform communication with the macro base station apparatus or the RRH without using cooperative communication so as to transmit and receive signals. For example, the macro base station apparatus receives an uplink signal from the mobile station apparatus located close to the macro base station apparatus in distance. For example, the RRH receives an uplink signal from the mobile station apparatus located close to the RRH in distance. Further, when the mobile station apparatus is located in the vicinity of the edge (cell edge) of a coverage of the RRH, a countermeasure against the same channel interference from the macro base station apparatus is required. By using a CoMP scheme in which adjacent base stations cooperate with each other as multi-cell communication (cooperative communication) with the macro base station apparatus and the RRH, a method has been considered which reduces or suppresses interference to the mobile station apparatus in the cell edge region.
Further, it has been considered that the mobile station apparatus receives signals transmitted from both the macro base station apparatus and the RRH using cooperative communication in the downlink, and transmits signals in a form suitable for either the macro base station apparatus or the RRH in the uplink. For example, the mobile station apparatus transmits uplink signals in transmission power suitable for receiving signals in a macro base station apparatus. For example, the mobile station apparatus transmits uplink signals in transmission power suitable for receiving signals in the RRH. This reduces unnecessary interference in an uplink, thereby improving the frequency utilization efficiency.
It is necessary for the mobile station apparatus to obtain, with respect to a reception process of the data signal, control information indicating a modulation scheme, a coding rate, a spatial multiplexing number, a transmission power adjustment value, allocation of resource, and the like which are used for data signals. In LTE-A, introducing a new control channel of control information regarding the data signal has been considered (NPL 1). For example, improving the capacity of all control channels has been considered. For example, supporting interference coordination in a frequency domain for the new control channel has been considered. For example, supporting spatial multiplexing for the new control channel has been considered. For example, supporting beamforming for the new control channel has been considered. For example, supporting diversity for the new control channel has been considered. For example, using the new control channel in a new type of carrier has been considered. For example, in the new type of carrier, not performing transmission of the reference signal which is common to all mobile station apparatuses within a cell has been considered. For example, in the new type of carrier, more reducing the transmission frequency of the reference signal which is common to all mobile station apparatuses within the cell than the conventional transmission frequency has been considered. For example, in the new type of carrier, demodulating signals such as control information by using a reference signal specific to the mobile station apparatus has been considered.
For example, as an application of beamforming, applying cooperative communication and transmission using a plurality of antennas to the new control channel has been considered. Specifically, it has been considered that a plurality of base station apparatuses and a plurality of RRHs, corresponding to LTE-A, apply a pre-coding process on signals of the new control channel and apply the same pre-coding process on a Reference Signal (RS) for demodulating signals of the new control channel. Specifically, it has been considered that a plurality of base station apparatuses and a plurality of RRHs, corresponding to LTE-A, map the signals and RSs of the new control channel to which the same pre-coding process is applied in a region of a resource in which PDSCH is mapped in LTE and transmit them. It has been considered that a mobile station apparatus corresponding to LTE-A demodulates signals of the new control channel which is subjected to the same pre-coding process by using a RS which is received and subjected to the pre-coding process and obtains control information. In this method, it is not necessary to exchange information about the pre-coding process that is applied to the signal of the new control channel between the base station apparatus and the mobile station apparatus.
For example, a method has been considered which configures signals of the new control channel by using different resources in the frequency domain as the application of diversity and obtains an effect of frequency diversity. In contrast, a method has been considered which configures signals of the new control channel by using same resources in the frequency domain when beamforming is applied to the new control channel.